Magnetically lockable universal vise



July 25, 1961 D. I. BOHN 2,993,395

MAGNETICALLY LOCKABLE UNIVERSAL VISE Filed Jan. 29, 1959 g/ g X 132 1 X l l 34 J .DO/VALg E' T H United States My invention relates to a novel universal vise which so supports a piece of work material that it may be advantageously positioned in any desired manner, and thereafter magnetically locked into this position.

Universal Vises of the magnetic type are well known in art, and are typically shown in my US. Patent No. 2,796,788, entitled Magnetically Lockable Universal Vise Support. In this type of vise support member, the vise clamp is carried by a spherical type member which is made of a magnetizable material, and is positioned to span two legs of a magnetic circuit. An energizing coil associated with this magnetic circuit may then be energized to pass flux through the first leg into the spherical member, and then to the second leg and back to the source of magnetic flux. With this type structure, a given locking power is available for a predetermined number of ampere turns.

My invention is specifically directed to a novel arrangement of the magnetic circuit in cooperation with the hemisphere wherein a far greater locking power is achieved, although the same number of ampere turns is utilized.

Furthermore, my novel structure is easily manufactured by the use of standard, readily available machines and of a minimum of parts.

More specifically, instead of placing the spherical type member in a magnetic circuit so that the flux enters only once and leaves only once with respect to the Spherical member, I form a magnetic structure having an E-shaped cross-section where the spherical member is positioned adjacent the center leg and completes the magnetic circuit from the center leg to the cylindrically shaped return magnetic circuit. This E-shaped cross sectional structure is preferably formed of a magnetic structure which is circular in shape, and has an annular opening therein for receiving a coil about a centrally projecting leg. Thus, the magnetic structure is essentially comprised of a central core and an outer tube with a coil interposed therebetween. The upper part of the magnetic structure seats the spherical member which supports a vise structure, while a high reluctance means is interposed between the two annular portions of the magnetic structure at its base so as to force magnetic flux to leave and re-enter at the bottom. This will serve as a means for sealing the vise magnetic structure to the bed of a machine without requiring any other means for securing the vise structure in a stationary manner.

It is to be noted that I have identified the means for carrying the vise as a spherical member. I intend to have the word spherical member broadly construed to generally mean any type of structure having at least a partially spherical portion which may be greater or less than a half sphere and may be a full sphere, and which may serve as a seat for a vise.

Accordingly, a primary object of my invention is to provide a novel magnetically lockable vise of relatively great locking power for a given number of ampere turns.

Another object of my invention is to provide a novel magnetically lockable vise which includes a magnetic structure having an E-shaped cross-section.

. A still further object of my invention is to provide a novel magnetic locking system for locking a member having at least a partially spherical shape in a predetermined position. l

A still further object of my invention is to provide a atent O 2,993,395 Patented July 25, 1961 novel magnetically lockable member and locking structure therefor which comprises an annular shaped magnetic structure having an annular coil therein and an E-shaped cross-section where the lockable member completes a magnetic path from a central leg to the outer portions of the magnetic structure.

These and other objects of my invention will become apparent from the following description when taken in connection with the drawings, in which:

FIGURE 1 is a cross-sectional view through the center line of my novel magnetically lockable vise structure.

FIGURE 2 is an exploded perspective view of the structure of FIGURE 1.

Referring now to the figures, the magnetically lockable vise structure is generally supported from some type of platform or bed 10 (FIGURE 1), which is preferably of some magnetic material such as steel or iron. Thus, the bed 10 could be the bed of a drill press to be used in connection with the novel lockable vise.

The vise structure for holding a piece of work material in a position may be of any desired type which is supported by the spherical member 12, which is made of a relatively high permeability material, such as mild steel or cast steel.

For purposes of illustration, the vise structure is shown in FIGURES 1 and i2 as comprising a rigid U-shaped member 14 which is bolted to a flat portion 16 of spherical member 12 by bolts 18 and 20. If desired, a low permeability plate of material such as aluminum may be placed between the member 14 and spherical member 12 to prevent passage of magnetic flux from spherical member 12 to the structure 14. The right-hand leg of U-shaped member 14 thread'ably receives a clamping screw 22 which has a pressure plate 24 at one end and a turning knob 26 at its other end. Clearly, a work piece may be inserted between the left-hand leg of U- shaped member 14 and pressure plate 24 and the knob 2i; and screw 22 thereafter rotated to fasten the work piece in a predetermined position.

If the position of the work piece is to be altered or adjusted, it has been previously necessary to loosen the work piece by screw 22, and thereafter try to hold it in a predetermined position, and then relock the piece. The essence of the present invention is to reposition the work piece without having to operate on the mechanical clamp.

To this end, spherical member 12 is supported by a steel ring 23 which has an internal outwardly sloping or chamfered surface 30 which, for example, forms a ten degree angle with respect to a line perpendicular to bed 10. The diameter of chamfered surface 30 is such that it will tangentially receive the spherical member 12 in supporting relationship, as typically shown in FIGURE 1. Preferably, the spherical member engages ring 28 at its upper portion to permit a maximum amount of rot-ation, and also to receive a maximum of the leakage flux of the energizing circuit. The ring 28 is then supported from a steel tube 32 by machine screws or any other rigid securing process, and the lower end of steel tube 32 is provided with circular grooves 34 which rest on bed 10 to support the complete structure from the bed.

The magnetic structure is then completed by a centrally positioned circular steel core 36 which has a machined away portion 38 therein for receiving a cylindrical energizing coil 40. The lower portion of core 36 is rigidly connected to the lower end of tube 32 by means of a welded bronze overlay 42 which, for example, may have a thickness of 0.046 inch and is welded to core 36. Preferably, the securing between tube 32 and core 36, which may be a shrink fit, is further such that dimension A is suflicient to cause some air gap, such as 0.007 inch, as will be described hereinafter.

Spherical member 12 is therefore positioned adjacent the end of the core 36 which may be considered the center leg of an E-shaped cross-sectional magnetic structure where the inclined surface 44 of the end of the core is spaced, for example, approximately 0.015 inch from the spherical member 12, this being indicated by dimension B. The incline of surface 44 may, for example, be of the order of from the horizontal, although this specific angle depends generally upon the diameter of the spherical member 12.

The electrical energizing circuit for coil is shown in FIGURE 1 as being taken from an A.-C. source 46 through rheostat 48, switch 49, step-down transformer 50 to the rectifier 52, which is connected across the leads of coil 40.

In operation, the control switch 49 is closed to connect A.-C. source 46 to transformer 50, and thus cause a D.-C. voltage to appear across the leads of coil 40. This energization of coil 40 will then set up a magnetic flux, as shown in dottedlines in FIGURE 1, which extends from core 36 through spherical member 12, ring 28, steel tube 34, and bed 10. Because of this magnetic flux, the spherical member 12 will be rigidly driven into extremely high pressure contact with the sloped surface 30 of ring 28, the pressure depending upon the downward force on hemisphere 12 and the slope of surface 30, to thereby rigidly position spherical member 12 in a predetermined position, and thus position the work piece carried by spherical member 12 in a predetermined position.

If it is desired to reposition the work piece, it is only necessary to either open switch 49 and thus deenergize the magnetic circuit, or increase the resistance of potentiometer 48 so as to substantially decrease the ampere turns of coil 40, and thus the magnetic holding force on spherical member 12, so that the spherical member may be gently repositioned, atlhough some resistance to motion is provided.

The magnetic circuit further operates to secure the complete magnetic structure in position with respect to bed 10 by virtue of the non-magnetic shim 42 which casues the flux to enter the bed after leaving tube 32, and thereafter enter the bottom of core 36, as shown in FIGURE '1.

In order to increase the flux density between the surface of bed 10 and the tube 32, the bottom surface of tube 32 is grooved by grooves 34. Thus, the force between tube 32 and bed 10 is increased, since this attractive force varies as the square of the flux density and the flux density is increased because of the decreased contact area.

The air gap A is provided to assure that all contact between the vise and the machine tool bed is at the bottom of tube 32, thus assuring a maximum of frictional resistance against rotational torque, or any overturning moment.

The large area at the bottom of core 36 gives a low flux density across all of air gap A, so very few ampere turns are required to supply the necessary M.M.F. for this small air gap.

Note, however, that standard mechanical clamping means may be employed in addition to, or in the absence of, the return magnetic flux for clamping the complete structure to a bed or surface.

The air gap B is provided to assure that all downward force of the spherical member results in frictional locking on the tapered seat 30, thus insuring maximum frictional resistance against rotational torque.

In testing a device of this general design, using a 4% diameter spherical member,. and with a coil of 2,700

ampere turns, the spherical member was locked so firmly as to resist slippage about a horizontalaxis at approximately 100 pound foot torque.

A further advantage of this structure will be apparent.

from its simplicity in construction. The steel tube 32 Cal may be a commercially available tube which need only be cut to length and thereafter grooved with the grooves 34 by a standard machining operation. Ring 28 and core 36 may similarly be formed by standard machining operations. The rigid securing, of ring 28 and core 36 to the tube 32 may obviously be accomplished by techniques well known in the art, such as employing a shrink fit.

In the foregoing, I have described my invention only in connection with preferred embodiments thereof. Many variations and modifications of the principles of my invention within the scope of the description herein are obvious. Accordingly, I prefer to be bound not by the specific disclosure herein, but only by the appending claims.

I claim:

1.. A magnetically lockable universal vise; said magnetically lockable universal vice comprising a vise structure, a central core, an outer tube, a ring, an energizing coil and a spherical member; each of said central core, outer tube, ring and spherical member being at least partially comprised of relatively high permeability material; said vise structure being connected to one portion of said spherical member; said ring having an annular sloping surface; said annular sloping surface receiving a second portion of said spherical member; said outer tube being concentrically positioned with respect to said central core; one end of said outer tube being rigidly connected to one end of said central core by nonmagnetic connecting means; the other end of said steel tube being rigidly connected to said ring and positioning said spherical member adjacent the other end of said central core; said central core having an energizing winding thereon for generating a flux from said central core, through said spherical member and to said ring.

2. A magnetically lockable universal vise; said magnetically lockable universal vice comprising a vise structure, a central core, an outer tube, a ring, an energizing coil and a spherical member; each of said central core, outer tube, ring and spherical member being at least partially comprised of relatively high permeability material; said vise structure being connected to one portion of said spherical member; said ring having an annular sloping surface; said annular sloping surface receiving a second portion of said spherical member; said outer tube being concentrically positioned with respect to said central core; one end of said outer tube being rigidly connected to one end of said central core by non-magnetic connecting means; the other end of said steel tube being rigidly connected to said ring and positioning said spherical member adjacent the other end of said central core; said central core having an energizing winding thereon for generating a flux from said central core, through said spherical member and to said ring; said one end of said tube extending beyond said one end of said central core and being supportable on a support surface.

3. A magnetically lockable universal vise; said magnetically lockable universal vice comprising a vise structure, a central core, an outer tube, a ring, an energizing coil and a spherical member; each of said central core, outer tube, ring and spherical member being at least partially comprised of relatively high permeability material; said vise structure being connected to one portion of said spherical member; said ring having an annular sloping surface; said annular sloping surface receiving a second portion of said spherical member; said outer tube being concentrically positioned with respect to said central core; one end of said outer tube being rigidly connected to one end of said central core by non-magnetic connecting means; the other end of said steel tube being rigidly connected to said ring and positioning said spherical member adjacent the other end of said central core; said central core having an energizing winding thereon for generating a flux from said central core, through said spherical member and to said ring; said steel tube serving as a return path for flux generated in said central core; said support surface having a relatively high permeability; said magnetic flux returning from said outer tube to said central core passing through said support surface; said one end of said outer tube having at least one annular groove therein for reducing the area of contact between the high permeability material of said outer tube and the high permeability of said support surface.

4. A magnetically lockable structure for holding an at least partially spherical member in a predetermined position; said structure including a central core member of magnetic material and an outer tubular member of magnetic material concentrically position with respect to said central core member; said central core member having an energizable Winding thereon; said tubular member having a first end and a second end; said first end of said tubular member having an annular surface which forms an angle with respect to the axis of said central core member; said annular surface tangentially receiving said at least partially spherical member along a line contact; said central core member having a first and second end; said first end of said central core member being positioned adjacent said at least partially spherical member; said energizable winding generating a flux in said central core member responsive to energization of said energizable winding; said flux circulating from said central core member, through said at least partially spherical member, through said tubular member and back to said central core member.

5. The device substantially as set forth in claim 4 wherein said second end of said tubular member is rigidly connected to said second end of said central core member.

6. The device substantially as set forth in claim 4 further including a rigid connecting means, said rigid connecting means being comprised of a non-magnetic member rigidly connected between said second end of said central core member and said second end of said tubular member.

7. The device substantially as set forth in claim 6 wherein said second end of said tubular member extends axially beyond said second end of said central core member; said extending second end of said tubular member being receivable by a support surface of magnetic material; said magnetic fiux generated by said energizable winding including said support surface of magnetic material in its magnetic circuit for securing said magnetically lockable structure to said support surface.

8. The device substantially as set forth in claim 7 wherein the annular surface of said second end of said tubular member which engages said support surface is provided with concentrically arranged annular grooves for reducing the contact area between said annular surface and said support surface.

9. The device substantially as set forth in claim 4 wherein said tubular member is comprised of a steel cylinder of constant internal and external diameter and an annular ring, said annular ring being connected to one end of said steel cylinder; said annular ring having said annular surface thereon receiving said at least partially spherical member.

10. The device substantially as set forth in claim 4, wherein said angle between said annular surface and said axis of said central core member is a relatively small angle.

References Cited in the file of this patent UNITED STATES PATENTS 1,066,951 Rowell July 8, 1913 1,665,226 Simmons Apr. 10, 1928 2,318,021 Lobosco June 12, 1945 2,510,634 Hull June 6, 1950 2,760,744 Watrous Aug. 28, 1956 2,787,874 Blood et a1. Apr. 9, 1957 2,796,788 Bohn June 25, 1957 

